Since then, scientists at Barcelona's Institut de Biologia Evolutiva at the University of Pompeu Fabra have been studying Snowflake's frozen blood and using it to sequence his genome.

In a new study, they announced a twofold discovery about Snowflake's genes that may help scientists understand how he became the only known albino of his species. An animal that does not produce melanin, resulting in little or no color in the skin, hair, and eyes, is considered an albino. (See more pictures of albino animals.)

Unusual Combination

First, the scientists pinpointed the exact genetic cause of Snowflake's albinism—a gene known as SCL45A2, which had previously been reported in albino mice, horses, and chickens, said study leader Tomas Marques-Bonet.

Second, and possibly more important, the scientists found that Snowflake was the result of inbreeding—an unusual practice for his species—which was likely the reason for the gorilla's unique coloration, according to the study, published May 31 in BMC Genomics.

The albino mutation is recessive, Marques-Bonet explained, meaning it becomes visible only if both parents pass the mutation on to a child. One of Snowflake's ancestors was likely the original carrier.

Because his parents were related—an uncle and a niece by the researchers' guess—their DNA contained some of the same genes, one of which happened to be the rare albinism mutation. (Get a genetics overview.)

Both the mutant gene and the inbreeding are rare occurrences for western lowland gorillas, and the combination that produced Snowflake isn't likely to happen again anytime soon.

"This explains why only one albino western lowland gorilla has ever been found," Marques-Bonet told National Geographic.